The present invention relates to an auto-ignition device for a vehicle crash protection device, e.g., an air bag, for passengers with a gas generator arranged in a housing structure. This gas generator features a primary igniting mixture, which is ignitable at a low ambient temperature and is embedded in a metal housing structure containing a window provided with a dam. This window is aligned toward a secondary igniting mixture or the gas generant compound.
U.S. Pat. No. 4,561,675 describes such an arrangement. In this connection, a metal housing structure containing a primary igniting mixture, which automatically ignites at an ambient temperature of approximately 177.degree. C., is mounted inside the closed gas generator housing and is aligned either toward the secondary igniting mixture, which is ignitable at approximately 343.degree. C., or toward the gas generant compound. The disadvantage of this specific embodiment is that the gas generator housing, which has a high heat capacity due to its material strength, must be heated to its ignition temperature in order to ignite the primary igniting mixture. In this case, the danger is that the dissipation of heat in case of fire can cause the automatic releasing action to be delayed too long, which can lead to a fragmentation of the housing.
Therefore, it is an object of the present invention to provide an auto-ignition device, so that when metals, especially light metals or other light construction materials are used for the gas generator housing, a reliable automatic releasing is attained under the influence of heat. Normally, such heat is not produced in the operational case or in storage, without the gas generator housing being subject to the danger of fragmentation. This danger is due, on the one hand, to the rising gas pressures in the inner space and, on the other hand, to the decreasing tensile strength, as the result of increasing temperature. At the same time, however, the density of the gas generator housing should remain intact.